The present invention relates generally to a topography simulation technique and more particularly to a topography simulation method for estimating a topography of a fine resist pattern which will be formed by selectively removing a part of a resist closely attached to a substrate and will then contract in a post-treatment step, and to a storage medium storing a program for carrying out this simulation method.
With recent development in shrinkage of LSIs, the resolution of lithography has almost reached a limit and it has become necessary to exactly estimate the resolution of lithography. The resolution in lithography depends on optical factors, but the superiority of the resolution in lithography determines whether a resist pattern significant in a subsequent step of etching, etc. can be provided.
Thus, when the resolution of lithography is estimated, it is conventionally necessary to simulate not only an image obtained by an exposure tool, but also photosensitization of a resist, post exposure baking (PEB), development, etc.
In general, an imaging model by a partially coherent optical system, proposed by Hopkins, Yeung, etc., is used as an imaging model by an optical system, and it is said that such imaging model has high precision. Photo-sensi models of novolak-based resists have been proposed by Dill, Mack, etc. There are many proposals regarding chemical amplified type resists. In addition, models of Fick, etc. have been proposed with respect to diffusion of a photo-active compound due to PEB. A string model, cell removal model, level set method model, etc. have been proposed as development models for effecting development in accordance with a photo-active compound distribution of a resist, which is calculated on the basis of the above models.
As stated above, the resist topography can be estimated with high precision by the imaging, photo-sensitization and development models. However, in the case of etching or ion doping, durability of a resist pattern needs to be increased by curing by means of UV radiation, hard baking, etc.
A resist pattern contracts and deforms due to curing treatment for increasing durability thereof. Consequently, an actual resist pattern topography differs from a topography obtained by resist development simulation.
In order to exactly simulate a resist pattern topography obtained after curing treatment such as hard baking, it is necessary to formulate causes of topography deformation due to contraction of the resist and to measure each parameter. It is, however, very difficult and time-consuming to produce complex physical models and measure parameters.
As has been described above, in the prior art, there is a problem in that a pattern topography of a resist used in etching or ion doping, which resist is patterned by photosensitization and development and then subjected to post-treatment, differs from a resist pattern topography obtained by resist development simulation because of deformation due to contraction in the post-treatment.
In order to simulate a resist pattern topography after the post-treatment, it is necessary to produce complex physical models and measure parameters.